Energy partitioning in the cell cortex.

Area of Science:

• Cell biology
• Biophysics
• Thermodynamics

Background:

• Living systems consume energy to maintain order far from thermodynamic equilibrium.
• Cellular patterns in chemical and mechanical activities are crucial for cell phenotypes and behaviors.
• The mechanism of intracellular energy partitioning remains poorly understood.

Purpose of the Study:

• To investigate how cells partition internal energy between chemical and mechanical activities in the cell cortex.
• To determine the relationship between energy partitioning, thermodynamic equilibrium, and cellular patterns.
• To explore the role of the Rho GTPase pathway in regulating cortical energy dynamics.

Main Methods:

• Measurement of entropy production rates in the chemical and mechanical subsystems of the cell cortex.
• Manipulation of the Rho GTPase pathway to induce diverse cortical patterns (pulses, choppy waves, labyrinthine/spiral waves).
• Analysis of Onsager reciprocity and energy partitioning across different pattern dynamics.

Main Results:

• Energy is proportionally partitioned between chemical and mechanical subsystems under Onsager reciprocity at lower activity levels (choppy waves).
• Entropy production rate is maximized in choppy waves within the range of reciprocity.
• Reciprocity is broken, and energy partitioning becomes differential as the cortex forms labyrinthine or spiral waves, uncoupling chemical and mechanical activities.
• Energy partitioning and reciprocity are governed by the interplay between chemical reaction and mechanical relaxation timescales.

Conclusions:

• Cellular energy partitioning is dynamically regulated and depends on the system's proximity to thermodynamic equilibrium.
• The breakdown of Onsager reciprocity signifies a shift in energy utilization strategies as cellular activity increases.
• The balance between chemical and mechanical timescales dictates how cells manage energy for pattern formation and function.